The relation between pulmonary function and cognitive functioning was investigated in a cohort of 3,036 Japanese-American men living in Hawaii. Pulmonary function, as indicated by forced expiratory volume in 1 second (FEV1), was measured at the baseline examination from 1965 to 1968. Cognitive function was assessed by the Cognitive Abilities Screening Instrument (CASI) test at least 23 years later (1991-1993). Baseline FEV1 was significantly correlated with follow-up CASI score (r = 0.22, p = 0.0001). Although the strength of the association was reduced by controlling for the effects of other factors, stepwise multiple linear regression showed that FEV1 during middle age was a significant predictor of CASI in later life, after taking into account the effects of age, education, stroke, sedentary job activity, nonmanual occupation, height, generation, and Japanese speaking ability. The mean CASI value was significantly greater for men whose FEV1 exceeded 2.8 liter compared with those whose FEV1 levels were in the lowest (<2.5 liters) quartile. Furthermore, the test on the effect of interaction between FEV1 and age was statistically significant (p = 0.0024), with subjects less than 55 years of age at the baseline examination showing a stronger direct association of FEV1 with CASI than the men aged 55 or older. These findings suggest that pulmonary function impairment may be associated with cognitive function impairment in later life.